Detection of GW170814
On August 14, 2017 the LIGO detectors in Hanford, Washington and Livingston, Louisiana, along with the Virgo detector in Cascina, Italy, detected a signal from the coalescence of two black holes, with masses 31 and 25 times the mass of the sun, merging into a more massive black hole that is 54 times the mass of the sun. This is the first detection by the joint LIGO-Virgo three detector network. A network of detector enabled localisation of the source through "triangulation" and gave access to the polarisation of the waves. The planned LIGO-India detector promises many fold improvement in source localisation accuracy as compared to the LIGO-Virgo network.
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The GW170814 detection paper on Physical Review Letters
Specific contributions by IUCAA researchers
- Matched Filtering
- A key analysis technique needed for every detection so far, pioneered at IUCAA
- Several refinements to the original analysis (e.g., to include multiple detectors)
- Development of efficient analysis techniques
- Network Analysis
- Optimal strategy to search for a signal in data from multiple detectors
- Estimation of Black Hole Binary parameters
- In improving the estimation accuracy of Black Hole spins
- Testing Einstein's General Theory of Relativity
- Detector Characterisation
- Application of Machine Learning to classify instrumental & astrophysical transients
- Development of an earthquake monitoring system
- Development of digital filters for LIGO seismic control system
- Application of Machine Learning for rapid documentation search
- Efficient methods for handling instrumental artefacts
- Towards building a LIGO detector in India
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- To dramatically improve the accuracy for estimation of location and orientation
- Developing search algorithms for Stochastic backgrounds
- A stochastic background from binary black-holes may be detectable by advanced LIGO in the next few years
Localisation errors for all the detections so far. GW170814 has significantly smaller localisation error thanks to the network.
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What was detected in the three detectors
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Parameters of the detected signal
Masses:
Masses of primary black holes: 30.5 and 25.3 (solar mass units)
Effective spin parameter primary black holes: -0.06 to 0.18
Mass and spin of the merged BH: 52 (solar units) and 0.7 (dimensionless)
Distance of event:
540 Megaparsec or 1.8 billion Light Years (1.7e+22 km)
Gravitational Wave signal:
Date of Arrival: 14 Aug 2017
Time of Arrival: 04:01 PM IST
Energy released in the form of GWs: equivalent of 2 solar mass (remember E = mc2)!
Source Localisation Accuracy 60 Square Degree (compared to 1160 Sq. Deg. with two LIGO detectors only)